This invention relates to a dynamic type MOS (Metal-Oxide-Semiconductor) memory device.
In a dynamic type MOS memory device in which the operation of selecting a word line and a data line is performed in accordance with a predetermined timing signal, this timing signal is brought into, for example, a high level at the time when the operation of a corresponding address buffer circuit has ended and when it has become possible to select one word line and data line by means of an address decoder circuit. In response to the high level of the timing signal, the gates of word line-and data line-selecting switch MOSFETs which are to be selected by the address decoder circuit are brought into a selection level such as the high level.
The timing signal can be delivered from a suitable control circuit which is started by a signal such as a memory start signal.
In this case, however, notice must be taken of the following:
In such a case where the timing signal is generated in the state in which the output signal level of the address buffer circuit is undetermined, the gates of the word line-and data line-selecting switch MOSFETs are supplied with signals of undesired level at the time when the operation of the address decoder circuit has not ended. As a result, the gates of the selecting switch MOSFETs of word lines to be unselected and data lines to be unselected are brought into the selection level, and a plurality of memory cells are selected at the same time.
Accordingly, there are required timing signals of desirable timing which operate the circuitry normally irrespective of the dispersion of the characteristics of elements in the address buffer circuit or the address decoder circuit and the variation of the element characteristics ascribable to temperature changes, supply voltage fluctuations, etc.
In case of utilizing the control circuit of the address buffer circuit, the address decoder circuit etc. as described above, the timing signal is generated with a delay time which is sufficiently longer than the maximum delay time that is determined by the dispersion and variation of the element characteristics. However, this forms a serious hindrance when it is intended to operate the circuit at high speed.